bra calculator uk

UK Bra Size Calculator

Use this free UK bra size calculator to get an estimated starting size. Enter your underbust and full bust measurements, then click calculate.

How the UK bra size calculator works

This UK bra size calculator uses a simple modern fitting method:

Band size is estimated by rounding your underbust to the nearest even UK band size.
Cup size is estimated from the difference between your full bust and band size in inches.
The result is a starting point for shopping and fitting, not a final diagnosis of fit.

In real life, bra sizing varies by brand, style, fabric stretch, and personal comfort. That is why a 34DD in one brand might feel like a 36D or 34E in another.

How to measure correctly at home

1) Underbust

Wrap a soft tape measure around your ribcage directly under your bust. Keep the tape level and snug, but not painfully tight. Exhale normally and record the number.

2) Full bust

Measure around the fullest part of your bust while keeping the tape level all the way around your back. Do not pull tight; the tape should just skim the body.

3) Use a non-padded bra (if possible)

A non-padded, well-fitting bra gives a more consistent measurement than a heavily padded bra or measuring over thick clothing.

UK cup progression reference

UK cup letters are not linear like many people assume. After D, UK sizing often continues as DD, E, F, FF, G, GG, and so on. Here is a quick reference from bust-band difference (inches):

Difference (in)	UK Cup
0	AA
1	A
2	B
3	C
4	D
5	DD
6	E
7	F
8	FF
9	G
10	GG
11	H

Sister sizes: useful when a bra almost fits

If your bra feels close but not perfect, sister sizing can help:

If band is too tight, go up one band and down one cup (for similar cup volume).
If band is too loose, go down one band and up one cup.

Example: 34E is close in cup volume to 36DD and 32F.

Common fitting mistakes in UK bra shopping

Choosing a larger band for comfort when the issue is actually cup depth.
Assuming D cup is always “large” regardless of band size (it is relative to the band).
Ignoring strap adjustment and strap placement.
Not checking gore tack (centre panel should sit close to the sternum in many styles).
Trying only one shape—balconette, plunge, full cup, and sports bras can all fit differently.

When to re-measure

It is worth rechecking your measurements if you notice discomfort, spillage, gaping cups, slipping straps, or riding band. Body changes, cycle changes, pregnancy/postpartum shifts, and training can all affect fit.

Final note

This bra calculator UK tool is designed for convenience and speed. Use the size as a starting point, then fine-tune with real try-ons. For the best comfort and support, a professional fitting in-store can still be very helpful.